1. Field of the Invention
Embodiments of the present invention generally relate to apparatus and methods of flow testing formation zones.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed, and the wellbore is lined with one or more strings of casing or a string of casing and one or more strings of liner. An annular area is thus formed between the string of casing/liner and the formation. A cementing operation is then conducted in order to fill the annular area with cement. The combination of cement and casing/liner strengthens the wellbore and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons.
After a well has been drilled and completed, it is desirable to provide a flow path for hydrocarbons from the surrounding formation into the newly formed wellbore. To accomplish this, perforations are shot through the casing/liner string at a depth which equates to the anticipated depth of hydrocarbons. Alternatively, the casing/liner may include sections with preformed holes or slots or may include sections of sand exclusion screens. Zonal isolation may be achieved using external packers instead of cement.
When a wellbore is completed, the wellbore is opened for production. In some instances, a string of production tubing is run into the wellbore to facilitate the flow of hydrocarbons to the surface. In this instance, it is common to deploy one or more packers in order to seal the annular region defined between the tubing and the surrounding string of casing. In this way, a producing zone within the wellbore is isolated.
Subterranean well tests are commonly performed to determine the production potential of a zone of interest. The test usually involves isolating the zone of interest and producing hydrocarbons from that zone. The amount of hydrocarbon produced provides an indication of the profitability of that zone.
Formation testing generally involves isolating the zone(s) of interest using a packer (or a plug). The packer is lowered to the target depth and actuated to seal against the wellbore, thereby isolating the zone to be tested. To arrive at the zone of interest, the packer is usually run through the production tubing string and then expanded against the wellbore. The ID of the production tubing is usually substantially smaller than the ID of the wellbore through the formation. This ID discrepancy requires packers having high expansion ratios which are typically inflatable packers.
These inflatable packers typically include an inflatable elastomeric bladder concentrically disposed around a central body portion such as a tube or mandrel. A sheath of reinforcing slats or ribs may be concentrically disposed around the bladder and a thick-walled elastomeric packing cover is concentrically disposed around at least a central portion of the sheath. The inflatable packers may be deployed in a wellbore using slickline, coiled tubing, threaded pipe, or wireline.
Pressurized fluid is pumped into the bladder to expand the bladder and the ribs outwardly into contact with the wellbore. A valve such as a poppet valve may be used to maintain the packer in an inflated state. After the packer is sufficiently expanded to seal the wellbore, the coiled tubing, jointed pipe, or wireline is detached from the packer and is retrieved from the wellbore. The inflated packer remains to operate as a seal.
To test multiple zones, a separate trip into the wellbore is performed to retrieve the packer and set a new one. The process of re-entering the wellbore and setting a new packer increases the time and effort of the operation.
There is a need, therefore, for apparatus and methods of testing multiple zones in one trip.